Reinforced sods have long been known in the art. Sod mats of groundcovers, flowers, and playing field grasses are among the examples.
Molnar (U.S. Pat. No. 5,224,290) discloses flower and groundcover sod mats reinforced with nylon sod reinforcements. Decker (U.S. Pat. No. 4,986,026) discloses tall fescue sod mats which are very large and employ planting mediums containing straw and sewage sludge. Molnar (application No. 07/745,224) discloses flower and groundcover sod mats reinforced with polypropylene sod reinforcements. Milstein (U.S. Pat. No. 4,941,282) discloses wildflower sod mats reinforced with polyester fabrics. McFarland (U.S. Pat. No. 4,786,550) discloses a lightweight seed mat formed with melt blown nonwovens. Walton (U.S. Pat. No. 4,934,094) discloses a grass sod reinforced with netting. Decker (U.S. Pat. No. 4,336,668) discloses a novel method of growing groundcover sods reinforced with synthetic netting. Muldner (U.S. Pat. No. 4,190,981) discloses a complex lightweight seed mat using complex expensive equipment. Airhart in HortScience 18(1), 89-91, 1983 discloses groundcover and flower sods reinforced with synthetic netting.
In general, sod mats reinforced with synthetic spunbond fabrics are excellent all purpose sod mats. They have very good sod mat production characteristics, good strength and are easy to handle. The current synthetic spunbond reinforced sod mats use the inherent strength of the synthetic fabric to reinforce them. This often results in higher synthetic resin consumption and other limitations discussed herein.
Sod mats employing natural reinforcements such as straw, bark, or water sensitive glues can decompose prematurely if harvest time or retail is delayed or if the planting medium is particularly biologically active. Furthermore, rate of degradation is generally difficult to control because of random environmental effects.
Sod mats employing synthetic netting for reinforcement can produce good sod mats. They do however, suffer from some important drawbacks. If the netting openings are large, harvest is usually delayed, while if the netting openings are small, the roots of the plants can be girdled. Neither leads to sod mats with both optimum sod mat production and growing characteristics. If the netting openings are large, the netting can also be troublesome to completely cover with planting medium.
In view of the above prior art, there still exists a need for sod mats with improved ease of ultimate disposal and improved garden friendliness. There still is a need for sod mats with the advantages of early harvest time, good "shelf life" stability, and easy handling and propagation. If the sod reinforcement degrades over time, there is a need to maintain good sod mat handling characteristics and "shelf life" stability. Furthermore, sod mats which place reduced demands on the strength of the stable fiber reinforcement are needed to reduce the stable fiber consumption and in general, to reduce costs. There exists a need for these new sod mats to be made with sod reinforcements which are easy to manufacture and handle in different and useful types of constructions. Objects of the current invention are then to develop sod mats with a select group of preferred sod reinforcements which are readily manufactured and are easy to handle. Another object of this invention is to develop sod mats that are easy to handle, have good "shelf life" stability, and place reduced demands on the stable fibers in the sod reinforcement. Another object of the invention is to develop sod mats with improved control of degradation which generally aids "shelf life" stability, garden friendliness, and ultimate disposal. It is also an object of this invention to develop a manufacturing process for these sod mats with good production characteristics.
Other objects and advantages of the current invention will become more apparent to those skilled in the art in view of the following description and examples.